• The Bulletin of The Korean Astronomical Society
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• v.44 no.1
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• pp.35.3-35.3
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• 2019

Blazars are a subclass of active galactic nuclei (AGNs) with relativistic jets aligned with our line of sight. The jet physics is yet to be understood, but can be studied with blazar variability (e.g., flares). The highly variable blazar 3C 279 has shown a general decline of its radio flux density since 2013, but the flux density has been increasing since 2017. To better understand physical properties of 3C 279 related with the flux variations, we analyze multi-frequency new radio data obtained with Korean VLBI Network (KVN), as well as archival data from Owens Valley Radio Observatory (OVRO) and Submillimeter Array (SMA). We measure the radio spectral variability and infer the relativistic jet properties of 3C 279. The high-cadence OVRO and SMA observations are used to construct detailed light curves of the source, and KVN data supplement the spectral coverage and allow us to locate the spectral break frequencies precisely. In this talk, we present our analysis results and interpret them using a blazar jet model.

• Journal of Astronomy and Space Sciences
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• v.38 no.4
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• pp.193-202
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• 2021

We present analysis results of Korean VLBI Network (KVN) four-band data for the highly variable blazar 3C 279. We measured the 22, 43, 86, and 129 GHz flux densities and spectral indices of the source using contemporaneous data taken over 5.6 years. We used the discrete correlation function to investigate correlations between the radio emission properties and those measured in the optical (2 × 10¹⁴ - 1.5 × 10¹⁵ Hz), X-ray (0.3-10 keV), and gamma-ray (0.1-300 GeV) bands. We found a significant correlation between the radio spectral index and gamma-ray flux without a time delay and interpreted the correlation using an extended jet scenario for blazar emission.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.2
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• pp.36.2-36.2
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• 2015

We report the first detection of linearly polarized emission at an observing wavelength of 350 mum from the radio-loud active galactic nucleus 3C 279. We conducted polarization observations for 3C 279 using the SHARP polarimeter in the Caltech Submillimeter Observatory on 2014 March 13 and 14. For the first time, we detected the linear polarization with the degree of polarization of $13.3%{\pm}3.4%$ (3.9sigma) and the electric vector position angle (EVPA) of $34.^{\circ}7{\pm}5.^{\circ}6$. We also observed 3C 279 simultaneously at 13, 7, and 3.5 mm in dual polarization with the Korean very long baseline interferometry (VLBI) Network on 2014 March 6 (single dish) and imaged in milliarcsecond (mas) scales at 13, 7, 3.5, and 2.3 mm on March 22 (VLBI). We found that the degree of linear polarization increases from 10% to 13% at 13 mm to 350 mum and the EVPAs at all observing frequencies are parallel within < $10^{\circ}$ to the direction of the jet at mas scale, implying that the integrated magnetic fields are perpendicular to the jet in the innermost regions. We also found that the Faraday rotation measures RM are in a range of $-6.5{\times}102{\sim}-2.7{\times}103$ rad m-2 between 13 and 3.5 mm, and are scaled as a function of wavelength:| {RM}| ${\backslash}propto$ {lambda }-2.2. These results indicate that the millimeter and sub-millimeter polarization emission are generated in the compact jet within 1 mas scale and affected by a Faraday screen in or in the close proximity of the jet.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.1
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• pp.36.4-36.4
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• 2021

블레이자는 제트가 관측자 시선방향과 나란하게 놓여있는 활동은하핵(AGN)으로 모든 파장대역에서 변광을 보이는 것이 주요 특징이다. 우리는 블레이자의 변광특성을 이해하기 위해 강한 변광을 보이는 천체인 3C 279를 연구대상으로 선정했고, 9년간의 X선 및 광학 데이터를 이용하여 이 천체의 광도와 스펙트럼 기울기 사이의 상관관계분석을 수행하였다. 이를 통하여, 시간에 따라 상관계수가 변한다는 것과 X선 변광이 광학변광보다 65일 앞선다는 것을 발견하였다. 이 발표에서는 one-zone SED 모형을 이용해 위의 현상들을 해석한 결과를 제시한다.

• KSBB Journal
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• v.19 no.4
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• pp.295-300
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• 2004

A marine bacterium for producing an collagenolytic protease was isolated from the southern sea of Korea and identified as Vibrio vulnificus and named as Vibrio vulnificus CYK279H. This strain producing an collagenolytic protease was showed high activity toward collagen and gelatin as substrate. The optimum initial pH, NaCl, and temperature for cell growth and protease production was 7.5, 2.0% and 25$^{\circ}C$, respectively. Optimization for collagenolytic protease production was composed of 0.3% D-galactose, 0.6% yeast extract, 4.0% gelatin, 0.2% (NH$_4$)$_2$SO$_4$, and 0.2 mM ferric citrate in artificial sea water. The maximum protease production was required gelatin and yeast extract. The collagenolytic protease production by Vibrio vulnificus CYK279H reached a maximum of 73 unit/l after the cultivation for 18 h under the optimized medium.

• Journal of The Korean Astronomical Society
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• v.48 no.5
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• pp.257-265
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• 2015

We present results of long-term multi-wavelength polarization observations of the powerful blazar 3C 279 after its γ-ray flare on 2013 December 20. We followed up this flare with single-dish polarization observations using two 21-m telescopes of the Korean VLBI Network. Observations carried out weekly from 2013 December 25 to 2015 January 11, at 22 GHz, 43 GHz, 86 GHz simultaneously, as part of the Monitoring Of GAmma-ray Bright AGN (MOGABA) program. We measured 3C 279 total flux densities of 22–34 Jy at 22 GHz, 15–28 Jy (43 GHz), and 10–21 Jy (86 GHz), showing mild variability of ≤ 50 % over the period of our observations. The spectral index between 22 GHz and 86 GHz ranged from −0.13 to −0.36. Linear polarization angles were 27°–38°, 30°–42°, and 33°–50° at 22 GHz, 43 GHz, and 86 GHz, respectively. The degree of linear polarization was in the range of 6–12 %, and slightly decreased with time at all frequencies. We investigated Faraday rotation and depolarization of the polarized emission at 22–86 GHz, and found Faraday rotation measures (RM) of −300 to −1200 rad m⁻² between 22 GHz and 43 GHz, and −800 to −5100 rad m⁻² between 43 GHz and 86 GHz. The RM values follow a power law with a mean power law index a of 2.2, implying that the polarized emission at these frequencies travels through a Faraday screen in or near the jet. We conclude that the regions emitting polarized radio emission may be different from the region responsible for the 2013 December γ-ray flare and are maintained by the dominant magnetic field perpendicular to the direction of the radio jet at milliarcsecond scales.

• Bulletin of the Korean Chemical Society
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• v.17 no.3
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• pp.279-284
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• 1996

Decay of the spin label attached to cytochrome c or to stearic acid has been measured by electron paramagnetic resonance (EPR) spectroscopy to monitor membrane oxidation induced by cytochrome c-membrane interaction. Binding of cytochrome c sequestered the acidic phospholipids and membrane oxidation was efficient in the order linoleic oleic>stearic acid for a fatty acid chain in the acidic phospholipids. The spin label on cyt c was destroyed at pH 7 whereas that on stearic acid embedded in the membrane was destroyed at pH 4, presumably due to different modes of cyt c-membrane interaction depending on pH. Interestingly, cyt c also interacts with phosphatidylethanolamine, an electrically neutral phospholipid, to cause rapid membrane oxidation. Both EPR and fluorescence measurements indicated that electrostatic interaction is at least partially responsible for the process.

• Proceedings of the Korean Magnestics Society Conference
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• 2007.05a
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• pp.279.1-279.1
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• 2007

• The Bulletin of The Korean Astronomical Society
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• v.39 no.2
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• pp.60.1-60.1
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• 2014

In the center of an Active Galactic Nuclei(AGN) is a supermassive black hole which accretes matter from its surroundings. The radio-loud AGN launch two relativistic jets perpendicular to the accretion disk which terminates into radio lobes located up to megaparsec away. Blazars form a small subset of radio-loud AGNs with one of two relativistic jets pointing toward the observer's line of sight. Many blazars often show flares at different frequencies. And these flares at different frequencies are known that they often correlate with each other. In 2013 December, there was a gamma-ray flare in 3C 279, one of the brightest blazars, Dec 2013. So we want to reveal that whether this flare correlates with radio flare or not, and where the flare originate. With polarization observation at radio frequencies, we can study the physical properties of the magnetic field in the innermost regions of the relativistic jets. Therefore, we have conducted polarization monitoring of this source from Dec. 2013 to Jun. 2014 with KVN(Korea VLBI Network) radio telescopes at 22, 43 and 86GHz. Here we present the initial results of the monitoring of 3C 279. We prospect that we can reveal the origin of this gamma-ray flare by comparing with our radio data.

• Journal of the Korean Applied Science and Technology
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• v.36 no.2
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• pp.676-684
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• 2019

The Pictet-Spengler reactions have widely known for the organic synthesis or biosynthesis of biologically active compounds, tetrahydro-${\beta}$-carbolines. We have developed the simple and efficient synthetic method for the synthesis of ${\beta}$-carbolines in water. Their chemical structures were characterized by nmr and UPLC/MS/QTOF. Calculated masses of compound 1 ($C_{17}H_{17}N_2$ 249.1392), 2 ($C_{17}H_{23}N_2$ 255.1861), 3 ($C_{19}H_{21}N_2O_3$ 325.1552) and 4 ($C_{19}H_{19}N_2O$ 279.1497) were almost identical with the detected masses of compound 1 (249.1315), 2 (255.1789), 3 (325.1460) and 4 (279.1364) respectively. Those synthesized four compounds showed strong antibiotic activity against the common E. coli.